1. Field of the Invention
The present invention relates to a level sensor which measures a level by utilizing a laser beam emitted from an electronic leveling apparatus.
2. Related Background Art
A prior art level sensor shown in FIG. 1 comprises a photo-sensing unit 4 which detects a laser beam emitted from an electronic leveling apparatus at a constant rotating speed and an LCD display unit 3. A signal detected by the photo-sensing unit 4 is processed by a signal processing circuit having functions of amplification, peak hold and comparison to display on the LCD display unit 3 a vertical deviation of the level sensor from the laser beam. A center notch 5 is formed on one side of a housing 1 at a vertical center position of the photo-sensing unit 4. Thus, when an operator moves the photo-sensing unit 4 of the level sensor to find the center position of the laser beam, he/she can make a mark by a pencil by using the notch 5.
In the prior art level sensor, the operator first coarsely moves the level sensor, and when he/she recognizes by an audio function that the level of the laser beam is in a vicinity of a reference position, he/she finely moves the level sensor toward the reference position while he/she monitors the display unit 3. In this case, the operator must pay great attention so that the level of the laser beam does not exceed the reference position. If the level of the laser beam exceeds the reference position from carelessness, the operator must finely move the level sensor toward the reference position in the opposite direction. As a result, the marking work is troublesome and time-consuming, and the operability is poor.